A process for hot rolling plates of ferritic stainless steel containing Nb known in the art is described in U.S. Pat. No. 4,374,683 which discloses a final rolling temperature in the finishing mill of 850.degree. C. or less, and the annealing of the resulting coil at temperatures of from 950.degree. to 1050.degree. C. However, the rolling process defined in the above-mentioned patent can be only used for steels having low carbon content, that is to say, not higher than 0.020% by weight, whereby it cannot be used for steels that are more difficult to roll.
Brazilian patents PI 8100131 and PI 8107666 describe processes for the production of strips which include adding Al to the ferritic stainless steel, such processes having the disadvantage of a double heat treatment of the hot rolled coils being necessary in order to avoid the so-called gold-powder defect that appears in cold rolled strips manufactured conventionally from ferritic stainless steel containing aluminum In the processes described in such Brazilian patents, the strips are hot rolled at a temperature higher than 900.degree. C. and are subjected to a first heat treatment at temperatures of from 700.degree. to 1100.degree. C., followed by a second heat treatment at temperatures of from 700.degree. to 900.degree. C. for diffusing the chromium, after which they are cooled down to a temperature lower than 200.degree. C.
The second heat treatment is carried out in order to allow the chromium to diffuse into the regions that become poor in this element due to the precipitation of chromium carbonitride during the initial heating up to temperatures of 1100.degree. C. If this treatment is not effected, a deterioration of the corrosion resistance will occur, which causes the gold-powder defect in the strips after the cold rolling. The above-mentioned processes have the further disadvantage that it is necessary to control the cooling temperature and that the lines of continuous annealing of hot rolled ferritic stainless steel strips must be especially designed for causing diffusion of the chrome in order to avoid the gold-powder defect. In such special lines, in addition to the furnaces and the cooling unit existing in conventional lines, one more furnace and one more cooling unit must be installed.